PROJECT ABSTRACT Motile cells are critical for the immune system, yet aberrant cell motility is the hallmark of tumors. How cells regulate movement is therefore an important issue. In this application, we explore the genetics of cell motility by experimentally manipulating in zebrafish a key component of the cytoskeleton? the actin-bundling protein L-plastin. L-plastin is normally expressed only in white blood cells, but is upregulated in many types of cancer cells and is frequently studied as an unfavorable prognostic marker for this disease. However the fundamental role of L-plastin in these motile cell populations remains unclear. For the study of this protein, the zebrafish provides an optimal combination of genetic and cellular features. Zebrafish have only one copy of the L-plastin gene, facilitating comparison with the corresponding locus in humans and mice. Genetic engineering in zebrafish is now highly efficient, allowing the rapid production of effective knock-out, knock-in and reporter lines. Finally, the transparent tissues of zebrafish allow live visualization of both normal and modified cell movements in almost any organ. Building on our previous work, this project will use zebrafish L-plastin knockout lines to examine the impact of this protein on cell division, cell adhesion, and immune cell migration. These studies will contribute to our understanding of L-plastin function in embryogenesis, immune response and tumor spread-- all contexts where proper cell migration is critical. In addition to evaluating the links between actin bundling, the cytoskeleton, and cell migration, the proposed work will train diverse undergraduates at our institution for future scientific careers.